Permanent magnetic chuck



. Dec. 30, 1941. J. T. BE ECHLYN PERMANENT MAGNETIC CHUCK 2 Shedts-Sheet1 Filed Aug. 6, 1940 M e l i i a l Plum 7 z 6 H m w W v IMF i a m 7/. GMM Dec. 30, 1941.

J. T. BEECHLYN PERMANENT MAGNETIC CHUCK Filed Aug. 6, 1940 llii 2Sheets-Sheet 2 11504226 (75/722 Z'EeeckQ v.

Patented Dec. 30, 1941 PERMANENT MAGNETIC CHUCK John '1. Beechlyn,Worcester, Mass, assignor to 0. S. Walker Co. Inc., a corporation ofMassaclnuetts Application August 6, 1940, Serial No. 351,564

Claims. (01. 175-367) This invention relates to magnetic chucks, whichare holding devices for magnetically securing ferric articles, whileundergoing manufacturing operations such as machinin rinding orpolishing. More particularly the invention involves a type of chuck inwhich, instead of the usually employed electrically energized winding, apermanent magnetic source is relied upon to furnish the needed magneticforce, such type having been rendered practical by recent discoveries ofalloys having exceptional coercive force.

Applied to holding devices the permanent magnet has several inherentadvantages over the electromagnet. However, when subject to the fullrequirements of the developed art in connection with standardizedmachinery, the permanent magnet chuck has thus far failed to equal, inseveral respects, the performance obtained from electro-magneticdevices. This refers both to the holding power or, at least, to thatpercentage of the total working surface in which an optimum ofattractive force can be obtained, and also to the degree of facilitywith which work may be released and removed from the chuck. In addition,it has been a characteristic of such chucks,

as hitherto commercially employed, that the rim of the top plate framingthe holding surface,

differs in magnetic polarity from the bottom of the chuck and themachine to which it is attached. This produces an undesirable zone ofattraction around the chuck, tending to cause accumulation of chips orsludge, and eventually a reduction of holding power, a condition thatdoes not occur with the ordinary electrochuck, in which the top frameand its entire external support have identical polarity. Also, thepermanent magnet chuck of the prior art tends to deteriorate with ageand use.

It is the general object of the invention to overcome these shortcomingsand to produce a permanent magnetic chuck that in all important respectswill be the equal of the electrochuck, while still retaining the specialadvantages incidental to the permanent magnet.

Another object of the invention is the provision of a permanent magneticchuck in which the holding power is greatly increased over prior artchucks of this type, and will even equal that of an electrochuck ofsimilar size.

. Another object is the provision of a permanent magnetic chuck whichwill not deteriorate with age and use, such deterioration in'priorchucks being due to displacement of a magnet with reit is indiscontinuous contact. In the present structure this is avoided bykeeping the magnets in fixed contact with the next contiguous fluxtransmitting members at all times.

A further object is the provision of a permanent magnetic chuck in whichthe top and bottom plates are of the same polarity, and in which suchplates are located in abutting relation, so that the side walls of thechuck serve as a return path in the magnetic circuit.

A still further object is the provision of a permanent magnet chuckhaving a stationary magnet and a reversible magnet, the latter beingcapable of parallel or series connection with the former, and thereversible magnet being equal to or greater in magnitude than thestationary magnet, so that when in series connection, the polarities ofthe work-holding members will be reversed, and work release and evenpartial demagnetization of the work will occur; and, when in parallelconnection, the flux of both magnets will be additive and thus both willcontribute to the flux in the work holding circuit.

Other objects and advantages of the invention will appear hereinafter.

Reference is to be had to the accompanying drawings, in which Fig. 1 isa front elevation of a chuck embodying the invention;

Fig. 2 is a top plan of the same;

Fig. 3 is a front elevation of the top of the chuck, showing the polesection separated in broken lines;

Fig. 4 is a section on line 4-4 of Fig. 2;

Fig. 5 is a broken away top plan of the bottom plate;

Fig. 6 is a front elevation of the bottom plate looking in the directionof arrow 8 in Fig. 5;

Fig. 7 is a side elevation of the bottom plate,

looking in the direction of arrow I in Fig. 5;

Fig. 8 is a top plan of the pole section; Fig. 9 is a front elevation ofthe pole section looking in the direction of arrow 8 in Fig. 8;

Fig. 10 is a side elevation of the pole section looking in the directionof arrow Ill in Fig. 8;

spect to a flux transmitting surface with which rotary magnet;

Fig. 16 is a partial side elevation of the assembled chuck, showing anend plate in section; and

Fig. 17 is a diagrammatic view of a modified, form of the chuck.

Referring to Fig. 1, the main parts of the chuck are shown as the topplate ill, bottom piateig secured directly to the top plate asby bolts14, pole section l 6,-soft nonmagnetic-metal spacing -l 3,-statlonarypermanent magnets as,

and'rotary or reversible magnetxassembly 22.

Ill

The top plate i comprisesian. integral n the shape of a flangedgrill,the. latter. hav- 3. Contlnuous-legs 28 extend. downward aces Iadjacent. the flanges or sidesli efiect are are correspondinglyapertured as at 50 for the reception of bolts 52. Soft iron top andbottom pieces 54 are drilled for the bolts 52 and these pieces clamp themagnets together to form a single magnet. This magnet is designed tohave an equal or slightly greater magnitude than that. of magnets 20combined.

The end faces of pieces 54 are counterbored as at 55 for the receptionof end plates 58, cne-cr'hoth of whiclsmay be. providedwith a handle 68'for turning the'mag'net assembly 22,

and latter is journaled in thecavity r d'br surfaces 32. 46. for.turning. movement J about-itsaxis- Thejhandleextends end vplate 6} asShOWn'inFig. 16. There is another end plate at the other'endf of thechuck to'plate 8i. 7

' The constructicm-asalroue described, and

; whichembodies apreferred form ofthe lawn-- continuations of'thesame,and form a-sn-ppcrt-.

for the top plate. The top plate is cast as one piece of soft iron, orother magnet flux carrying material, and this is also true of the polesection and bottom plate, although clearly any or all of these partscould be machined from iron blocks. The bars 24 form slots 29 whichextend across,

the body from points just short of the inner faces of the legs 28.

The base plate I2 is bored and counter-sunk at 30 to provide for boltsl4, and on its top surface it has a circular depression. 32 bored orotherwise machined out. The pole section I6 is shown in detail in Figs.8-10, and comprises a base 34 having a top surface which extendsupwardly from both longitudinal edges as at 36, these edges merging intoa flat top surface 38. The bottom of the pole section is bored out atcomplementary to the depression 32 in the bottom plate.

A row of parallel pole pieces 42 having flat tops, project from thesides 36, and each pole piece continues across the flat top 38 to theother side thereof. The pole pieces are not as long as the base 34 iswide, and as shown in Fig. 9, they are evenly recessed or inset from theedges of the base, as at 39.

Fig. 3 shows how the pole section I6 is assembled with relation to thetop plate I 0, the former being moved in the direction of the arrow, sothat each pole piece will be inserted in a slot between cross-bars inthe top plate. The topsof the pole pieces are adapted to lie flush withthe top surface of the top plate. The bottom plate i2 is then bolted tothe top plate, and the legs 28 rest directly on the bottom plate, aswill be clear from Fig. 1.

Permanent magnets 20 of Alnico or some other permanent magnet alloy areplaced between the bottom plate and the pole section, as shown in Fig.1, and the latter rests directly on the magnets which in turn rest onthe bottom plate. The magnets 20 will be of a length to extend thelength of the chuck.

With the parts as described, soft metal 43, as Babbitt metal or lead, ispoured into the insulating spaces between the pole pieces and the bars24, thus sealing the assembly against entrance of foreign matter andsecuring the members in fixed relation. This of course leaves agenerally cylindrical opening caused by surfaces 32, 40, thru the chuck.The magnets 20 are of such a width that they stop short of the opening,leaving air gaps 4|.

The rotary, or reversible magnet pieces 41, I3,

tion, provides a; return path; for. the flux emanating from themagnets-2c, sees, thru the-sides 25 legs 28,130 the bottom plate i2, sothe entire exteripr ofythe chuck body except for pole pieces 42 willalways have the same polarity,

thus avoiding the collection of chips, sludge, and I other particles onthe rim of the top plate, and which has been unavoidable heretofore inchucks of the permanent magnet type. At the same time, the chuckbody'afiords interior space for an adequate total section ofpermanent'magnetic material, a result not heretofore obtainable. Hence,a holding power is achieved, in the relatively small space commerciallyrequired of a chuck, at least as great as in an electrochuck of the sameor similar outside dimensions. Factors contributing to this result willbe described below.

The reversible magnet assembly 22 provides a novel arrangement forarbitrarily causing complete release of the work from the chuck. Thus,when magnet 22 is located with the pole uppermost which is similar insign to the top poles of magnets 20. the fluxes of all three magnets arein parallel, and a powerful flux flows thru the pole pieces, into thework, thru the top plate and the side walls to the bottom plate, thusclosing the circuit. However, if magnet assembly 22 be given a turn,the'flux thereof will be in series with that of magnets 20, and thetotal flux volume will be reduced by nearly one-half. The flux excessfrom magnet 22 will now cause a reversal of polarities in thework-holding members, and thereby release of the work. Since the fluxvolume in the magnet 22 may be designed to exceed in any degree that ofmagnets 20 combined, a partial demagnetization of the residual magnetismof the work piece may also be effected.

The invention thus involves the division of the total magnetic sourceinto two slightly diflering quantities, each of these sources beingnormally magnetically connected with the work-holding chuck members sothat flux in the circuit traverses the two sources in parallel to holdthe work, means being provided for reversing connections for the largersource, whereby the total flux volume will be reduced by nearlyone-half, and the major portion of this flux will traverse the twosources in series, resulting in a reversal oi. polarities in thework-holding members, and release of the work.

In the described form the source having fixed connections has been shownas consisting of two separate magnets respectively situated on each sideof the reversible magnet.- While this arrangement is desirable, it willbe apparent that the operating principle in no way depends on suchseparation, and that a single larger magnet can be employed as the fixedsource and disposed in any position within the chuck so long as it isproperly connected with the basic ferric members.

However, the present symmetrical arrangement oflers the advantageparticularly where subject to the limits of chuck height encountered inpractice, that a large diameter of the reversible magnet is renderedpossible through its central disposition without involving anyencroachment on the flux conducting ferric sections of the chuck. Alsothe division and disposition of the fixed magnet, which is of relativelylow height compared with the height of a well proportioned coil in anelectrochuck, permits the use of a relatively large section in the gridbars 24 where they join the sides 25 of the top plate ill. The sectionat this juncture ordinarily constitutes a bottle neck" in the fiuxconduit in chuck design, and the gain afforded by the presentarrangement accounts in a measure for the high degree of holding powerthat has been attained even with the work surface fully loaded.

It will be noted that iron pieces 54 overlap the magnets 41, 48, seeFig. 14, and therefore the magnet is never movable with respect to acontacting fiux transmitting member. Hence the lines of force in themagnet are never .disturbed, and partial demagnetization is avoided. Bythis structure the chuck is insured against deterioration due to use andage, such deterioration being a fault of all prior art permanent chucksin which a magnet is in movable contact with a flux transmittingsurface.

A modification of the invention is shown in Fig. 17, wherein stationarymagnets II are arranged to transmit the fiux laterally.

This arrangement has some advantage in connection with certain grades ofmagnet alloy having high coercive force but a relatively low remanence,since it allows the use of a total magnet section greater than could bedeployed across a single plane within the side walls of the chuck, as inthe priorly described design. The reversible magnet in this case hasbeen divided into two separate magnets 12, 12, and any desired linkageor gearing may be applied to cause both magnets 12 to turn together.

The top plate 14 is substantially the same as plate ill, but the feedingsection may be slightly smaller. Flanges or sides 16 provide the returnfiux path to bottom plate 18, which is bored to receive the magnetassemblies 1!. Pole section 80 is somewhat diiferent in shape from polesection ii, the pole pieces extending laterally beyond the sectionitself. Soft metal 82 insulates the pole section from the top plate atthe working area, but the magnets are directly connected between thesetwo members. However, the operation of this device is generally the sameas that shown in Fig. 1, and it is not thought necessary to repeat it.

In the foregoing reference has been made to different magnitudes of thestationary and reversible magnets. This does not necessarily refer tophysical dimensions but rather to the magnetic magnitudes involved.Although the dimensions of the magnets will in some measure infiuencetheir magnetic magnitudes, the insertion of a high reluctance in anymagnetic circuit will afiect the magnetism of the circuit. Hence a thinnon-magnetic plate may be placed to transect the circuit of one of themagnets, as the stationary magnet, and thus cause a difierentlal in thepower of the circuits of the stationary and reversible magnets.

Having thus described my invention and the advantages thereof, I do notwish to be limited to the details herein disclosed, otherwise than asset forth in the claims, but what I claim is:

l. A permanent magnet chuck comprising a plurality of magnetic membershaving a magnetic interconnection at one area and a magnetic insulationat a separated area, said interconnection including a pair of magnets,said magnets being adapted to be relatively reversible with relation totheir poles one magnet being fixed in said chuck and the other beingrotatable.

2. A permanent magnet chuck comprising a base, a top plate, said topplate having integral depending sides connected to said base to form aflux path, said top plate sides providing a space therebetween, a fixedmagnet and a pole section in said space, a pole piece on said polesection extending into said top plate and insulated therefrom to form awork-holding surface, a second magnet in said space, said second magnetbeing mounted for rotary movement about an axis intermediate of itspoles whereby it may be positioned selectively in parallel or series,fiux circuit with said first magnet, said base, top plate, and polesection being of ferro-magnetic material.

3. A permanent magnet chuck comprising a combined bottom plate and topplate, the former being generally plane and the latter being in the formof an inverted U, with its legs connected to said bottom plate, slots insaid top plate, a fixed magnet and a pole section within the spaceformed by said bottom and top plates, said magnet being located betweensaid bottom plate and said pole section, pole pieces on said polesection extending into said slots, said pole section and said bottomplate being complementarily recessed to provide a bore, and a reversiblemagnet journaled in said bore.

4. A permanent magnetic chuck comprising a work holding surface, amagnet fixed with relation to said surface, and a second magnet adaptedfor rotation, said magnets being in parallel circuit when said secondmagnet is in one position of rotation and in series circuit when saidsecond magnet is in another position of rotation.

5. A permanent magnetic chuck having a fixed magnet and a rotary magnet,whereby said magnets may be situated in series or parallel fiuxcircuits, said rotary magnet being of greater fiux magnitude than saidfixed magnet, whereby when in parallel, both magnets pass flux in asingle direction through a work-holding circuit, and when in series asmall portion of the fiux from the rotary magnet is oppositely directedthrough the work-holding circuit.

6. In a device of the class described, a housing of ferro-magneticmaterial comprising a top, side walls, and a base, a flux transmittingmember in said housing and projecting into relation with the top to forma work surface therewith, said housing and member being magneticallyseparated at said surface, a permanently fixed magnet having two polesand resting on said base with a fixed magnetic connection from one poleto said base, said member resting on and rigidly supported by saidmagnet in fixed magnetic connection with the other pole of said magnet,a second magnet, and magnetic connections between the individual polesof said second magnet and the member and base, said last namedconnections being selectively reversible with relation to said memberand base, whereby theflux of said second magnet may be directed inparallel with the flux of said first named magnet or in oppositionthereto.

7. A device as recited in claim 6 wherein said 5 second magnet has aflux magnitude sufiiciently greater than that of said fixed magnet tocause a reversal flux through said member and housing, said reversalflux being large enough to overcome any substantial holding effect dueto residl0 ual magnetism in a work piece on said surface, therebypermitting easy removal of the work piece from the device.

8. A permanent magnetic holding device comprising a pair of soft ironmembers magnetically 15 separated to form a work-holding surface, afixed magnet adapted to form a magnetic circuit with said members and awork piece held on said device, and a second magnet capable of havingits poles reversibly connected with respect to said 20 work surface andsaid fixed magnet, said second magnet having a flux magnitudesufliciently greater than that of said fixed magnet to cause a reverseflux through said members, said reverse flux being large enough toovercome any 25 substantial holding eifect due to residual magnetism insaid work piece, thereby permitting easy removal of the work from thedevice.

9. In a work-holding device of the class described, the combination oftwo ferric members jointly forming a magnetic work-holding surface, aferric base, one of said members being fixedly seated on said base, atwo pole magnet also fixedly seated on said base with one of its polesconnected thereto, the other of said members being fixedly seated on theopposite pole of said magnet, whereby-a magnetic circuit including saidmembers, magnet, base, and a work piece adapted to be held to saidsurface is provided; with a second magnet, and magnetic connectionsbetween the poles of said second magnet and the other of said membersand said base. said magnetic con,- nections being selectivelyreversible, whereby the flux of said second magnet may be selectivelydirected in parallel with the flux of said fixedly seated magnet or inopposition thereto.

10. A device as recited in claim 9 wherein said second named magnet hasa flux magnitude sufiiciently greater than the flux of said fixedlyseated magnet to cause a reversal fiux through said ferric members andwork piece, when said fluxes are directed oppositely, said reversal fluxbeing large enough to overcome any substantial holding effect due toresidual magnetism in the work piece, thereby permitting easy removal ofthe latter from the device.

JOHN '1'. BEECHLYN.

